If I need to keep my browser open for an extended period of time. I'd like to enter my Primary Password to access the password manager. But then after (x) minutes it should lock out and prompt you for the Primary Password again if you need to access the password manager.

When you enter the Primary Password when prompted then you log in to the Software Security Device (Password Manager) and you unlock the passwords and have access to the stored passwords until you log out of the Software Security Device. You can logout of the Software Security Device (Password Manager or about:logins) by clicking Cancel in a Primary Password dialog like you get when you click the eye icon to reveal a password on the about:logins page (you may have to close and reopen about:logins) and Firefox will prompt you once again for the PP when required to access the logins.

You can inspect the current login state of the Software Security Device in the Device Manager.

• Settings -> Privacy & Security -> Certificates ->
  Security Devices: Software Security Device: Log Out button in the right sidebar

You may have to zoom out to make the sidebar show properly.

What are you referring to here? Primary password is only used for login to firefox account and sync nothing more. Firefox password doesn't timeout.

Nope. Primary password was formerly Master Password. https://support.mozilla.org/en-US/kb/use-primary-password-protect-stored-logins https://support.mozilla.org/en-US/kb/primary-password-replacing-master-password

Multiple devices/profiles: Primary passwords are set locally and are not synced between profiles or devices. If you use more than one device or profile, those use separate primary passwords.

You can use it with Sync though. https://support.mozilla.org/en-US/kb/using-primary-password-sync

I guess this more of a feature request. It would be nice for there to be a timeout feature